My 1.4 Fiesta Zetec is running really rich at the moment. I am lucky if I crack 31mpg round town, yet, get 40-41mpg on the motorway... I occasionally get the Engine Managment Light come on, which if you clear with a DTC reader, wont come back on for months on end. Error code seems to signify Lambda Sensor, but I was wondering if anyone else had any other suggestions before I fork out for them?

Sounds like lambda sensor not giving correct air/fuel mixture hence why you're going through so much fuel. My brother had a similar problem and after changing the lambda sensor 3 times the garage he was taking it to noticed he had a big hole in his back box. After that was replaced it was fine